// Opacity
@for $i from 0 through 20 {
  .#{$prefix}opacity-#{$i * 5} {
    opacity: 0.05 * $i;
  }
}
// box-shadow
.#{$prefix}box-shadow {
  box-shadow: 0 2rpx 4rpx 0 rgba(0, 0, 0, 0.03), 0 2rpx 12rpx -1px rgba(0, 0, 0, 0.02), 0 4rpx 8rpx 0 rgba(0, 0, 0, 0.02);
}